The present invention relates to image processing and more particularly to automated microscopy systems and methods for locating and re-locating objects of interest in an image.
The present invention is particularly well suited for use in an automated microscopy system for analyzing biological objects (such as blood cells) on a microscope slide. Generally, with such an automated analysis system, cells on a slide are initially scanned and a digitized image of the cell configuration is generated. This image is processed to determine, or extract various features of the scanned cells. Based on these identified features, the cells are then classified by the system. Often, certain of the cells are either unclassifiable (by the system), or for other reasons, require further analysis, either by a human operator or by further machine processing. Records of such cells, identified as objects of interest, are stored so that those cells may be subsequently re-located for the required further analysis. After the slide (or a number of additional slides) has been analyzed on a first pass, the system automatically returns to selected (or flagged) areas having objects-of-interest for further analysis. In most instances, the slides must be removed from the microscope stage prior to the further analysis. In order to perform this further analysis, accurate and repeatable re-location of the objects-of-interest on the microscope slide is essential.
Several designs for accomplishing these objectives have been described and implemented in the prior art, such as that shown in U.S. Pat. No. 3,851,972, issued Dec. 3, 1974. The method taught by this patent re-locates individual objects (cells, specifically) through computer memorization of the slide location in the cassettes (or slide identification indicia) and coordinate signals representative of a specific cell's location on the slide. In the commercial implementation of this patented design, cell location is memorized as stage X and Y coordinates, (as taken from step counters) referenced to the instrument's "Home" position, i.e., the position of the stage when the slide may be loaded onto the stage. When the slide is reloaded onto the microscope stage, a servo controlled mechanical assembly returns the slide to its original position based upon the memorized coordinates. This (and all other known methods for object re-location) requires highly repeatable and precise repositioning of the stage's home position relative to the instrument's optical axis and equally precise repositioning of the slide in the stage's slide holder on re-loading. These requirements arise in the open-loop nature of such relocation methods and in practice result in excessively demanding tolerances on mechanical components and electrical drive circuitry, with correspondingly great hardware cost.
In other applications, such as numerical-controlled machine tools, and in some research automated microscopes, closed-loop positioning servos incorporating linear encoders or similar sensors are used to provide precise positioning of an element. While the degree of precision permitted by such systems would satisfy the requirements for most automicroscopy applications, the hardware cost is too high to permit their use in commercial automated microscopes.
It is an object of the present invention to provide an improved automated microscopy system and method for locating and re-locating objects-of-interest in an image.
It is another object to provide an improved microscopy system and method for automatically analyzing objects-of-interest on a microscope slide and subsequently re-locating those objects-of-interest for further analysis.